The present invention relates generally to an airfoil seal arrangement, and more particularly to an arrangement of a gas turbine engine having airfoils with squealer tips.
A gas turbine engine comprises a compressor that pressurizes air, a combustor that mixes pressurized air from the compressor with fuel and ignites the resulting fuel-air mixture, and a turbine that extracts energy from the ignited mixture downstream of the combustor. Both the compressor and turbine includes a plurality of airfoil elements, often in multiple stages. These airfoil elements comprise rotor blades and stator vanes located in airflow passages generally defined by gas turbine engine casings, rotors, and shrouds. Rotor blades rotate relative to stator vanes that generally remain stationary with respect to the body of the gas turbine engine. Airflow leakage around the tips of blades and vanes at respective outer and inner airflow diameters of airflow passages reduces gas turbine engine efficiency. To avoid this, a compressor is conventionally constructed with a minimal gap between blade or vane tips and adjacent stationary or rotating surfaces, respectively. Blades and vanes need not form perfect air seals with these adjacent surfaces, but are designed to reduce gas bleed. To this end, squealer tips of blades and vanes are commonly manufactured with labyrinth or knife-edge seals. Some blades or vanes with knife-edge seals use thin or tapered “squealer” tips. During a break-in cycle of the gas turbine engine, these squealer tips are abraded by contact with adjacent engine components. Stator vane squealer tips, for instance, make contact with an adjacent inner airflow diameter shroud or rotor land surfaces within the gas turbine engine. Frictional contact between the shroud or rotor land and the stator vane squealer tip abrades the squealer tip until only a uniform minimum gap remains between the stator vane and the rotor. This abrasion process can melt blade or vane squealer tips, and sometimes liberates abraded debris from the stator vane, rotor surface, or both. Liberated debris can reduce component lifetimes within the gas turbine engine.